<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        var num = 0;
        // 就是在函数中再次调用函数
        function fn() {
            num++;
            // 必须在递归函数中给定停止条件
            console.log(5);
            if (num == 5) {
                return;
            }
            fn();
        };
        fn();
    </script>
</body>

</html>